Recent improvements in portable electronic devices have increased the demand for batteries with a high energy density in order to increase the longevity of these devices. A variety of lithium secondary batteries have been studied to meet these demands. Many of these batteries have explored the use of lithium metal anodes and carbonaceous anodes. Theoretical calculations show that lithium metal may be able to provide a higher energy density than a carbonaceous anode.
Batteries having lithium metal anodes are difficult to commercialize because they generate dendritic lithium on the surface of the lithium metal during charge and discharge cycle. The dendritic lithium can grow toward the cathode through the separator and cause an internal short in the battery. This short can result in a dangerous release of heat. Additionally, current can concentrate on the dendrites causing a localized deposition of lithium on the anode. This localized deposition can reduce the cycling efficiency of the battery.
Further, lithium metal anodes can reduce the cycling performance of a battery. Conventional organic electrolytes in contact with lithium metal get reduced and can form a passivation layer on the anode. When other anode materials are employed, the formation of the passivation layer stops or slows when the surface of the active material is covered by a stable passivation layer. However, the growth of the dendritic lithium permits the passivation layer to continue forming and increases the surface area over which the passivation layer must be formed. The continued formation of the passivation layer reduces the battery's coulombic efficiency and can accelerate electrolyte degradation. There is a need for a secondary battery that can take advantage of lithium metal anodes.